simpleflying.com
It's an expensive conversion option, according to this article most of converted 747 owner choose not to take it. However seems the article hinted it's available if some cargo Airliners want to choose it.
According to IAI Bedek, they can provide variety of cargo loading options in their highlight page line. Still their video shown cargo door in rear fuselage, that's seems in line with what simple flying article on 747 conversion above.
I believe the problem with A380 is on how to make the upper deck for efficient cargo holding. 747 conversion so far seems not touching the upper deck for Cargo holding, and only for crew accommodation. However this resulted that the 747 lower deck volume is larger than A380 lower deck. Make it more attractive for cargo Industry.
Airbus need to think how to create more attractive conversion for A380, if they want it to continue flying in future.